This invention relates to spring contacts of a type which are commonly used on circuit boards of touch switch selector telephone instruments. Other uses for spring contacts in accordance with the invention, will be apparent from the following description.
The touch switch telephone number selector units of the type which are currently being manufactured have a circuit board located in back of the panel on which the individual digit selector switch buttons are located and this circuit board has mounted thereon a plurality of spring contacts which extend past fixed contact pins mounted in the circuit board. Each time one of the individual switch buttons is pressed to select a digit when a number is being called, all of these switches are flexed by a mechanism which engages the ends of the spring contacts and moves them towards or away from their associated contact pins. Obviously, the spring contact which is used on circuit boards under these conditions must be capable of a vast number of cycles of flexure without failure, for the reason that telephone instruments are designed to yield many years of service and the springs will be flexed several times when each number is selected and a call is being made.
At present, these circuit boards are manufactured by inserting a mounting pin into the circuit board and thereafter spot welding a spring contact blade to the mounting pin. It is also necessary to insert a separate support pin adjacent to the mounting pin which serves to support the spring blade during flexure. While present manufacturing processes produce spring contacts which have the requisite reliability and satisfy all electrical requirements, the manufacturing cost is relatively high because of the fact that two insertion operations and one assembly operation (the welding of the spring contact to the mounting pin) are required for each spring contact. The instant invention is directed to the achievement of an improved spring contact which will satisfy all the electrical and mechanical requirements of the application and which will result in a substantial reduction in manufacturing cost.
In accordance with the principles of the instant invention, the spring contact is manufactured by stamping and forming a strip of suitable spring metal so that the contacts can be fed to an insertion machine and automatically inserted into the circuit board. The individual spring contacts comprise an elongated spring blade having a mounting plate portion integral therewith at one end thereof. The mounting plate portion extends partially along the length of the blade and has at one end thereof an integral supporting pin which is intended to be mounted in the circuit board and to support the spring blade when the contact is flexed. A mounting pin is provided at one end of the spring blade which consists of laterally extending legs on the blade itself and on the mounting plate. In addition, supporting flanges are provided on the mounting plate which bear against the surface of the circuit board when the contact is inserted into the holes in the circuit board. The supporting flanges serve to protect the spring contact in the event that any downward force is imposed on the contact after insertion.
It is accordingly an object of the invention to provide an improved spring contact having integral mounting means for mounting on a circuit board. A further object is to provide an improved spring contact in continuous strip form. A further object is to provide a contact having an integral support pin which serves to support the blade during flexure.